Essays and addresses / by professors and lecturers of the Owens College, Manchester.
- Victoria University of Manchester
- Date:
- 1874
Licence: Public Domain Mark
Credit: Essays and addresses / by professors and lecturers of the Owens College, Manchester. Source: Wellcome Collection.
Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.
127/576 page 107
![nr.] called the antichthon, was placed between the earth and the central fire, probably, as Aristotle says, to make up the number of orbits to ten. The distances from the centre were—to the antichthon, 3 ; to the earth, 9; the moon, 27; the sun, 81; and so on. This scheme was based entirely upon abstract con- siderations, and utterly fails to account for the observed phenomena. Eudoxus of Cnidos, who flourished about 370 years B.C., first imported scientific accuracy into astronomy. He built an observatory on a hill, that he might have a better view of the stars, and observed their positions at rising and setting compared with definite points of the zodiac. He calculated the sun's distance to be nine times that of the moon ; but so uncertain was he on this point, and so enthusiastic in his astronomical studies, that he declared he would willingly be con- sumed, like Phaethon, if he might first approach so near the sun that he might be able to discover its size and figure. Aristarchus of Samos, who was the first to propound a theory of the universe similar to the Copernican, lived about a hundred years after Eudoxus. He proposed a most ingenious method to find the sun's distance, in which the distance of the moon was taken as the base line, and his method remained for many centuries the only one available. He remarked that when the moon was half full {^>iypTo\Lo% aeXrjvr)), the earth is on the plane of the circle which divides the light from the dark half. And the line joining the centres of the sun and moon is perpendicular to this plane. In the diagram, Fig. 2, let E and s be the centres of the earth and sun,](https://iiif.wellcomecollection.org/image/b21727910_0127.jp2/full/800%2C/0/default.jpg)
